This 200-901 practice question tests your understanding of network fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO are benefits of using VLANs in a network? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reducing the size of broadcast domains
VLANs reduce the size of broadcast domains (A) and improve security by isolating traffic (C). They do not reduce the number of collision domains (B) – collision domains are reduced by switches, not VLANs. VLANs do not simplify Layer 3 routing (D) – they often require routing between VLANs. They do not guarantee faster routing (E).
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Reducing the size of broadcast domains
Why this is correct
VLANs segment the network into smaller broadcast domains.
Related concept
Access ports place end devices into a single VLAN.
✗
Simplifying Layer 3 routing
Why it's wrong here
Routing between VLANs is required.
✓
Improving network security by isolating traffic
Why this is correct
VLANs can isolate sensitive traffic.
Related concept
Access ports place end devices into a single VLAN.
✗
Reducing the number of collision domains
Why it's wrong here
Switches create collision domains per port, not VLANs.
✗
Guaranteeing faster routing performance
Why it's wrong here
VLANs do not guarantee performance.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-901 questions on switching, trunking, and access-port configuration.
Network Fundamentals — This question tests Network Fundamentals — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Reducing the size of broadcast domains — VLANs reduce the size of broadcast domains (A) and improve security by isolating traffic (C). They do not reduce the number of collision domains (B) – collision domains are reduced by switches, not VLANs. VLANs do not simplify Layer 3 routing (D) – they often require routing between VLANs. They do not guarantee faster routing (E).
What should I do if I get this 200-901 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-901 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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